首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2532篇
  免费   143篇
  国内免费   7篇
耳鼻咽喉   15篇
儿科学   116篇
妇产科学   72篇
基础医学   363篇
口腔科学   53篇
临床医学   174篇
内科学   488篇
皮肤病学   51篇
神经病学   108篇
特种医学   429篇
外科学   187篇
综合类   69篇
一般理论   1篇
预防医学   129篇
眼科学   114篇
药学   177篇
  1篇
中国医学   7篇
肿瘤学   128篇
  2023年   11篇
  2022年   25篇
  2021年   55篇
  2020年   33篇
  2019年   38篇
  2018年   34篇
  2017年   46篇
  2016年   40篇
  2015年   59篇
  2014年   92篇
  2013年   111篇
  2012年   117篇
  2011年   133篇
  2010年   96篇
  2009年   88篇
  2008年   92篇
  2007年   108篇
  2006年   90篇
  2005年   87篇
  2004年   88篇
  2003年   76篇
  2002年   62篇
  2001年   29篇
  2000年   16篇
  1999年   22篇
  1998年   91篇
  1997年   86篇
  1996年   85篇
  1995年   75篇
  1994年   48篇
  1993年   64篇
  1992年   12篇
  1991年   13篇
  1990年   24篇
  1989年   53篇
  1988年   43篇
  1987年   46篇
  1986年   54篇
  1985年   68篇
  1984年   38篇
  1983年   32篇
  1982年   29篇
  1981年   31篇
  1980年   39篇
  1979年   8篇
  1978年   20篇
  1977年   23篇
  1976年   21篇
  1975年   22篇
  1914年   1篇
排序方式: 共有2682条查询结果,搜索用时 15 毫秒
991.
992.
A simple, efficient, precise and accurate absorbance ratio method have been developed for the estimation of eprosartan mesylate and hydrochlorothiazide in pure and in fixed dose combination. In this method, UV spectra of eprosartan mesylate and hydrochlorothiazide were overlayed which involves the formation of Q-absorbance equation at 249.1 nm (isobestic point) and 274.5 nm, the max of hydrochlorothiazide. Both the drugs obeyed Beers law in the concentration range of 6-36 μg/ml and 1-10 μg/ml for eprosartan mesylate and hydrochlorothiazide, respectively. The accuracy of the method was determined by recovery studies and was found to be in the range of 102.29-103.10% and 99.52-101.60% for eprosartan mesylate and hydrochlorothiazide, respectively. The method was validated as per ICH guidelines and statistically. The method showed good reproducibility and recovery with % RSD less than 2. The method was found to be simple, economic, accurate and reproducible and can be used for routine analysis of eprosartan mesylate and hydrochlorothiazide in pure and in fixed dose combinations.  相似文献   
993.
994.

Purpose

Hematopoietic PBX interacting protein (HPIP), a scaffold protein, is known to regulate the proliferation, migration and invasion in different cancer cell types. The aim of this study was to assess the role of HPIP in ovarian cancer cell migration, invasion and epithelial-mesenchymal transition (EMT), and to unravel the mechanism by which it regulates these processes.

Methods

HPIP expression was assessed by immunohistochemistry of tissue microarrays containing primary ovarian tumor samples of different grades. OAW42, an ovarian carcinoma-derived cell line exhibiting a high HPIP expression, was used to study the role of HPIP in cell migration, invasion and EMT. HPIP knockdown in these cells was achieved using a small hairpin RNA (shRNA) approach. Cell migration and invasion were assessed using scratch wound and transwell invasion assays, respectively. The extent of EMT was assessed by determining the expression levels of Snail, Vimentin and E-cadherin using Western blotting. The effect of HPIP expression on AKT and MAPK activation was also investigated by Western blotting. Cell viabilities in response to cisplatin treatment were assessed using a MTT assay, whereas apoptosis was assessed by determining caspase-3 and PARP cleavage in ovarian carcinoma-derived SKOV3 cells.

Results

We found that HPIP is highly expressed in high-grade primary ovarian tumors. In addition, we found that HPIP promotes the migration, invasion and EMT in OAW42 cells and induces EMT in these cells via activation of the PI3K/AKT pathway. The latter was found to lead to stabilization of the Snail protein and to repression of E-cadherin expression through inactivation of GSK-3β. We also found that HPIP expression confers cisplatin resistance to SKOV3 cells after prolonged exposure and that its subsequent knockdown decreases the viability of these cells and increases caspase-3 activation and PARP proteolysis in these cells following cisplatin treatment.

Conclusions

From these results we conclude that HPIP expression is associated with high-grade ovarian tumors and may promote their migration, invasion and EMT, a process that is associated with metastasis. In addition, we conclude that HPIP may serve as a potential therapeutic target for cisplatin resistant ovarian tumors.
  相似文献   
995.
Our objective was to compare the onset and duration of a single dose of pantoprazole or omeprazole on maximally stimulated gastric acid secretion. This double-blind, randomized, placebo-controlled study involved 36 healthy adults and utilized continuous pentagastrin infusion to stimulate acid secretion after administration of pantoprazole, 40 mg, omeprazole, 20 mg, or placebo. Gastric aspirates were collected over 24 hr and analyzed for volume, pH, and hydrogen ion concentration, and gastric acid outputs (GAO) were calculated. Comparison between GAO and intragastric pH was performed. Pantoprazole resulted in significantly greater inhibition of GAO than omeprazole. Mean cumulative 24-hr GAO was 164 ± 130 mEq for pantoprazole versus 283 ± 159 mEq for omeprazole (P = 0.031). Pantoprazole patients reached and maintained GAO levels below the 10-mEq/hr threshold at 5.7 hr, whereas omeprazole patients never reached this threshold. We conclude that pantoprazole significantly suppressed gastric acid secretion compared to omeprazole. Comparisons between pH and GAO showed that GAO was a more appropriate measure of gastric acid secretion than intragastric pH. This work received financial support from Wyeth Pharmaceuticals.  相似文献   
996.

Objectives:

To assess the influence of total or selective REM sleep deprivation on the dopamine transporter (DAT) densities and sleep patterns of healthy volunteers.

Design:

Prospective study.

Setting:

Evaluation of polysomnography recordings and DAT density after 4 nights of selective REM sleep deprivation followed by 3 nights of sleep recovery compared to a control group and a group that was subjected to 2 nights of total sleep deprivation. Single positron emission computed tomography and [99mTc]TRODAT-1 were used to assess the cerebral DAT density in the striatum at baseline, after REM sleep deprivation and total sleep deprivation as well as after sleep recovery. Blood was collected daily to examine prolactin and estradiol levels, which were correlated with dopaminergic activity.

Patients or Participants:

Thirty healthy male volunteers ranging from 19 to 29 years of age were randomly assigned to one of three experimental groups after giving written informed consent (10 non-sleep deprived, 10 total sleep deprived, and 10 REM sleep deprived).

Measurements and Results:

Four nights of REM sleep deprivation and 2 nights of total sleep deprivation induced distinct and heterogeneous patterns of sleep recovery. No significant modulation of DAT availability was observed within groups. In the recovery nights, changes in cortisol, prolactin and estradiol concentrations were significantly correlated with specific sleep stages in the total and REM sleep deprived groups. In addition, DAT density was positively correlated with estradiol concentration and inversely associated with SWS latency only after total sleep deprivation.

Conclusion:

Our study demonstrates that although sleep deprivation did not promote significant alterations in DAT density within the striatum, there were significant correlations among transporter availability, hormonal concentrations and sleep parameters.

Citation:

Martins, RCS; Andersen ML; Garbuio SA; Bittencourt LR: Guindalini C; Shih MC; Hoexter MQ; Bressan RA; Castiglioni MLV; Tufik S. Dopamine transporter regulation during four nights of REM sleep deprivation followed by recovery – an in vivo molecular imaging study in humans. SLEEP 2010;33(2):243-251.  相似文献   
997.
Introduction: Acellular nerve allografts (ANAs) yield less consistent favorable outcomes compared with autografts for long gap reconstructions. We evaluated whether a hybrid ANA can improve 6‐cm gap reconstruction. Methods: Rat sciatic nerve was transected and repaired with either 6‐cm hybrid or control ANAs. Hybrid ANAs were generated using a 1‐cm cellular isograft between 2.5‐cm ANAs, whereas control ANAs had no isograft. Outcomes were assessed by graft gene and marker expression (n = 4; at 4 weeks) and motor recovery and nerve histology (n = 10; at 20 weeks). Results: Hybrid ANAs modified graft gene and marker expression and promoted modest axon regeneration across the 6‐cm defect compared with control ANA (P < 0.05), but yielded no muscle recovery. Control ANAs had no appreciable axon regeneration across the 6‐cm defect. Discussion: A hybrid ANA confers minimal motor recovery benefits for regeneration across long gaps. Clinically, the authors will continue to reconstruct long nerve gaps with autografts. Muscle Nerve 57 : 260–267, 2018  相似文献   
998.
999.

Study Objective

The aim of this study was to compare the parental attitudes and beliefs about human papillomavirus (HPV), cervical cancer, and HPV vaccine between urban and rural areas, India.

Design

Cross-sectional.

Setting

Mysore, India.

Participants

Parents of school-going adolescent girls.

Interventions

Parents completed a self-administered questionnaire.

Main Outcome Measures

Attitudes and beliefs about HPV, cervical cancer, and HPV vaccine.

Results

A total of 1609 parents from urban (n = 778) and rural (n = 831) areas participated in this study. Most of the parents had never heard about HPV (73.6%), did not know that their daughters could get an HPV infection (62.7%) or cervical cancer (64.1%) in the future, and believed that HPV vaccine was not effective (67.1%). Parents living in the urban area were more likely to believe that HPV infection (adjusted odds ratio [aOR], 2.69; 95% confidence interval [CI], 1.43-5.06) and cervical cancer (aOR, 2.68; 95% CI, 1.83-3.91) could cause serious health problems than those living in the rural area. The odds of agreeing that HPV vaccination will make girls sexually active was lower among urban than rural parents (aOR, 0.55; 95% CI, 0.33-0.94). There was no significant difference among parents in the urban and rural areas in their beliefs about susceptibility of their daughter to HPV infection or cervical cancer, and beliefs about the safety and ability of HPV vaccine to protect against cervical cancer.

Conclusion

Rural parents might be reluctant to recommend behaviors that can help prevent HPV infection and cervical cancer such as HPV vaccination for their daughters.  相似文献   
1000.

Objectives

To compare patient outcomes using the Pediatric Index of Mortality-3 (PIM-3) model with PIM-2 model for children admitted to the intensive care unit.

Methods

We prospectively recorded the baseline characteristics, variables of PIM-3 and PIM-2 at admission, and outcomes of children ≤17 years over a period of 11 months. We used Area Under Receiver Operating Characteristics (AU-ROC) curves and Goodness-of-fit (GOF) tests to determine which of the two models had better discrimination and calibration.

Results

Out of 202 children enrolled, 69 (34%) died. Sepsis and pneumonia were the common admitting diagnoses. The AU-ROC was better for PIM-3 (0.75) as compared to PIM-2 (0.69; P=0.001). The GOF-P value was 0.001 for both models, that indicated poor calibration of both (P<0.001). The AU-ROC curves were acceptable across different age and diagnostic sub-groups.

Conclusion

PIM-3 had better discrimination when compared to PIM-2 in our unit. Both models had poor calibration across deciles of risk.
  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号